Hello there, Garmac!
I see what you mean.
Unfortunately there is no 'official' package for Microsoft Edge web browser.
Nor is it in the "user" repository called KCP - similar to AUR on Arch Linux.
If I get some time and the know-how, and manage my time, I could create an installable package for you by using this command inside terminal:
$ kcp -u
$ kcp -s 'name-of-package'
$ kcp -i microsoft-edge(-stable)
-- Or something like that. ;-)
Please try to use the pre-installed KCP tool in the meantime to search for software that is not in the 'official' KaOS repositories.